Now, for my Rig, powered with i5 7400 + GTX 1080, 2HDDs and 1SSD, How much wattage do I need for these?

For your PC I would suggest getting a Seasonic 650W unit and that should be enough for your CPU + a future GPU upgrade. That is assuming your GPU upgrade is within GTX 1080 - GTX 1080 Ti levels of power consumption.

I don't have any plans upgrading my GPU (I think, up to 2 years) but I am looking forward for the Ryzen 2700X.

If you plan to upgrade to a Ryzen 7 2700X and maybe pair it with a high-end videocard like the level of a GTX 1080 Ti, then 650W should still be adequate. But I would be more comfortable bumping up to a 750W PSU since the Ryzen 7 2700X can consume 140 watts of power under heavy load.

nachambahan ka lang din ng lemon. lahat ng second hand items naman may risk. nobody is to blame but yourself in reality. I have experienced the same thing as well pero hindi psu but just the same, second hand item.

Kung out of stock ang Seasonic Focus+ Gold SSR-650FX... consider paying slightly more and get the 750W model (SSR-750FX). Prices between the higher capacity models are not that big and sometimes the money you save by waiting weeks or a month for stock to arrive is not worth it.

Pero kung sila din walang stock on hand it means nagkaubusan na sa distro / supplier and no choice but to wait or buy a different PSU.

Personally at this point in time, mas prefer ko na mag Seasonic Focus+ Gold even if its the SSR-550FX model compared to getting let's say the M12II-620. Laking bagay kasi yung 10 year warranty it trumps everything hehe.